To conserve energy and control heating costs, it has always been important to have a well insulated house. Windows are a major source of heating inefficiency. Accordingly, it is desirable to improve the seal around window openings, especially during cold winter months. Various methods which have been developed, such as the use of storm windows, can still be improved. For instance, multiple pane windows can be used but tend to be expensive. Also, balloon type bags inflated between the storm window and the window's exterior surface have been used. The edges of the air bags can engage the planar surface of the window's glass panes. This defeats the purpose of the air bag since heat is thereby allowed to transfer through the window. Also, in larger windows, these air bags collapse or buckle and do not adequately seal the window.